Influence of Herbicide Triasulfuron on Soil Microbial Community in an Unamended Soil and a Soil Amended with Organic Residues.

The effect of organic amendments and pesticides on a soil microbial community has garnered considerable interest due to the involvement of microorganisms in numerous soil conservation and maintenance reactions. The aim of this work was to assess the influence on a soil microbial community of the simultaneous application of the herbicide triasulfuron at three doses (2, 10, and 50 mg kg-1), with an organic amendment [sewage sludge (SS) or green compost (GC)]. Dissipation kinetics, soil microbial biomass, dehydrogenase activity (DHA) and respiration, and the profile of phospholipid fatty acids (PLFAs) extracted from the soil, were determined in unamended (S) soil and amended (S+SS and S+GC) ones. Triasulfuron dissipation followed the single first-order kinetics model. Half-life (DT50) values were higher in the amended soils than in the unamended one for the 10 and 50 mg kg-1 doses. The dissipation rates were lower in the S+GC soil for the three herbicide doses applied. In general, soil biomass, DHA and respiration values increased in SS- and GC-amended soils compared to the unamended one. DHA values decreased (S and S+SS) or increased (S+GC) with the incubation time of soil with herbicide at the different doses applied. Respiration values increased with the herbicide doses applied and decreased with the incubation time, although maximum values were obtained for soils treated with the highest dose after 70 days of incubation. PLFA analysis indicated different effects of triasulfuron on the soil microbial community structure depending on the organic amendments. While the increasing triasulfuron doses resulted in deeper alterations in the S soil, the time after triasulfuron application was the most important variation in the S+SS and S+GC soils. The overall results indicate that the soil amendment has an effect on herbicide dissipation rate and the soil microbial community. Initially, a high dose of triasulfuron had detrimental effects on the soil microbial community, which is important in the case of the long-term use of this compound.

Desenvolvimento de bezerros leiteiros alimentados com silagem de leite de transição: I - Trato digestivo / Development of dairy calves fed silage transition milk: I - Digestive tract

Avaliou-se o desenvolvimento do trato digestivo de bezerros Holandeses aleitados com silagem de leite de transição. Foram utilizados 18 animais, com peso corporal inicial médio de 36,50kg (±4,03), alimentados individualmente em baias com concentrado, feno de Cynodon sp., água e suplemento mineral oferecidos ad libitum. O delineamento experimental foi inteiramente ao acaso, com três tratamentos e seis repetições. Os tratamentos consistiram em leite integral e silagem de leite de transição diluída em água ou misturada em leite, correspondendo a quatro litros diários divididos em duas refeições, durante 59 dias. Aos 60 dias, os bezerros foram abatidos e realizaram-se pesagens do trato digestivo e medidas histológicas das papilas ruminais. O sistema de aleitamento não interferiu nos consumos de concentrado e matéria seca total e no desenvolvimento de papilas ruminais (P>0,05). A silagem de leite de transição diluída em água resultou em menor peso corporal, menor peso corporal vazio e absoluto do abomaso e maior desenvolvimento intestinal. O aleitamento com silagem misturada em leite não comprometeu o desenvolvimento corporal e do trato digestivo até 60 dias de idade, representando alternativa ao aleitamento com leite...

This study aimed to evaluate the development of the digestive tract of Holstein calves which suckled milk from silage transition. We used 18 animals, with an average initial body weight of 36.50kg (±4.03), individually housed in pens with concentrate, hay Cynodon sp., water and mineral supplement offered ad libitum. The experimental design was completely randomized with three treatments and six replications. Treatments consisted of whole milk and silage transitional milk, diluted with water or mixed with milk, corresponding to four liters per day divided over two meals during 59 days. The food intake was monitored daily and weighed every week after the supply of liquid diet in the morning. At 60 days, the calves were slaughtered and the digestive tract was weighed and histological measures of rumen papillae were taken. The nursing system did not affect the consumption of concentrate and total dry matter and the development of rumen papillae (P>0.05). The silage transition milk diluted in water resulted in lower final body weight, lower body weight and absolute emptiness abomasum and intestinal further development. Milk transition silage mixed in milk did not affect the development of the digestive tract and body until 60 days of age, representing an alternative to milk...

Effect of spent mushroom substrate applied to vineyard soil on the behaviour of copper-based fungicide residues.

The effect of the addition of spent mushroom substrate (SMS) to the soil as an amendment on the distribution and/or fate of copper from a copper-based fungicide applied to a vineyard soil in La Rioja (N. Spain) was studied. The study was carried out on experimental plots amended or not with SMS at rates of 40 and 100 t ha(-1). The variation in total Cu content in the topsoil (0-10 cm) and in the soil profile (0-50 cm), and the distribution of Cu in different fractions of the topsoil were studied as a function of the dose of Cu added (5 and 10 kg ha(-1)) and of the time elapsed since application (0-12 months). In addition, the changes in the chemical properties (solid organic carbon (OC), dissolved organic carbon (DOC) and pH) of the soils were studied. A greater capacity for Cu retention by the amended soils than by the unamended one was observed only when the fungicide was applied at the high dose. No effect of the amendment rate was noted on this retention capacity. The metal content in the topsoil decreased over time in step with the disappearance of the OC in the amended soil due to its oxidation, mineralization and/or leaching. This decrease in total Cu content was possibly due to the formation of soluble Cu complexes with the DOC, which facilitated its transport through the soil. A re-distribution of Cu in the different soil fractions was also observed over time, mainly from the organic to the residual fraction. The results obtained indicate that the increase in OC due to the application of SMS at the rates used does not lead to any significant increase in the persistence of Cu in the soil over time. Of greater interest would be the assessment of the risk for groundwater quality, owing to possible leaching of the fungicide enhanced by the SMS when SMS and Cu-based fungicides are jointly applied to vineyard soils.